yarn: Upgrade packages

- eslint 7.25
- ra-language-german 3.13
- react-admin 3.15
- react-dom 17.0
- react-scripts 4.0

Change-Id: Iad982cf647470bc16194000519a72c401009c9fa

src/i18n/de.js

@@ -1,6 +1,6 @@
 import germanMessages from "ra-language-german";
 
-export default {
+const de = {
   ...germanMessages,
   synapseadmin: {
     auth: {
@@ -351,3 +351,4 @@ export default {
     },
   },
 };
+export default de;